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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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3.3.2 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.
Содержание GT540
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