Lge Internal Use Only - LG -E510 Service Manual

3. TECHNICAL BRIEF
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 and 850
mode transmitting. This design guideline shows only UMTS 2100 applications.

LGE Internal Use Only

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