Only For Training And Service Purposes - LG GW620 Servise Manual

3.3.2 UMTS TRANSMITTER
The UMTS TX path begins with differential baseband signals (I and Q) from the MSM device.
These analog input signals are amplified, filtered, and applied to the quadrature up-converter mixers. The up-
converter output is amplified by multiple variable gain stages that provide transmit AGC control. The AGC
output is filtered and applied to the driver amplifier; this output stage includes an integrated matching
inductor that simplifies the external matching network to a single series capacitor to achieve the desired 50-
Ω interface.
The RTR6285 UMTS output is routed to its power amplifier through a bandpass filter, and delivers fairly high-
level signals that are filtered and applied to the PA. Transmit power is delivered from the duplexer to the
antenna through the switch module.
The transceiver LO synthesizer is contained within the RTR6285 IC with the exception of the off-chip loop
filter components and the VC-TCXO. This provides a simplified design for multimode applications. The PLL
circuits include a reference divider, phase detector, charge pump, feedback divider, and digital logic
generator.
UMTS TX Using only PLL1, the LO generation and distribution circuits create the necessary LO signals for nine
different frequency converters. The UMTS transmitter also employs the ZIF architecture to translate the signal
directly from baseband to RF. This requires FLO to equal FRF, and the RTR6285 IC design achieves this without
allowing FVCO to equal FRF.
The RTR6285 IC is able to support UMTS 2100/1900/1800/1700/900 and 850 mode transmitting. This design
guideline shows UMTS 2100, UMTS1900 and UMTS850 applications.
Copyright © 2009 LG Electronics. Inc. All right reserved.

Only for training and service purposes

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3. Technical Brief
GW620
LGE Internal Use Only