- 18 -
3.3 UMTS Mode
3.3.1 Receiver
The UMTS duplexer receiver output is routed to LNA circuits within the RTR6280 device. The UMTS
Rx input is provided with an on-chip LNA that amplifies the signal before a second stage filter that
provides differential downconverter. This second stage input is configured differentially to optimize
second-order intermodulation and common mode rejection performance. The gain of the UMTS
frontend amplifier and the UMTS second stage differential amplifier are adjustable, under MSM
control, to extend the dynamic range of the receivers. The second stage UMTS Rx amplifiers drive the
RF ports of the quadrature RF-tobaseband downconverters. The downconverted UMTS Rx baseband
outputs are routed to lowpass filters having passband and stopband characteristics suitable for UMTS
Rx processing. These filter circuits allow DC offset corrections, and their differential outputs are
buffered to interface shared with GSM Rx to the MSM IC. The UMTS baseband outputs are turned off
when the RTR6280 is downconverting GSM signals and on when the UMTS is operating.
3.3.2 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 upconverter mixers. The
upconverter 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 RTR6280 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 RTR6280 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 RTR6280
IC design achieves this without allowing FVCO to equal FRF.
LGE Internal Use Only
Copyright © 2008 LG Electronics. Inc. All right reserved.
Only for training and service purposes
Z3X-BOX.COM
Summary of Contents for KF310
Page 174: ...Note Z 3 X B O X C O M ...